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| We'll Call it Metisse........ |
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| John Rudd:
--- Quote from: sbwhart on August 14, 2013, 04:41:53 AM --- the copper doesn't seem right as you said its probably expanding with heat and making things to go a little to tight. Stew --- End quote --- If the cylinder is copper and is expanding surely the bore will become bigger? :scratch: |
| vtsteam:
Actually copper has a relatively low coefficient of expansion compared to "aluminum". Which would explain increasing tightness. However, expansion depends on the particular aluminum alloy. And Aluminum is the metal used in most iron cylinders in IC engines. However - a special alloy. -- also cast iron rings do most of the active hard contact. Also lubrication is different in an IC engine than in a hot air engine. Hot air engines don't like oil in the displacer -- so it is difficult to lubricate the power piston. Graphite is a good material for power pistons therefore. Also the natural graphite in a cast iron power cylinder might be a help for hot air engines -- something I've been thinking about since I have been casting iron. |
| Stilldrillin:
Hmmm....... Graphite. That's a thought. Thanks Fellas. :thumbup: I will clean the synthetic 5-W30 oil from the piston/ cyl assembly, and try it with graphite lube, tomorrow. David D |
| Bluechip:
Hi Dave Happy Birthday, it seems .... :clap: :clap: :clap: here's to many more .... That motor looks a bit of a strange configuration ... :scratch: I think you are right to put a deflector on it. Otherwise you have a hot end and a 'very nearly as hot' end ... not good ... The other thing that strikes me is that the power piston works against gravity, assuming the power stroke is upwards, so it's at a disadvantage to start with. At the risk of being grossly misinterpreted, have you tried it lying down, ie. horizontal. That way the flame would tend not to heat the ally fins and the piston would not be acting against gravity. Net images can be a bit iffy, but just how heavy is the piston/con-rod ?? Rod looks brassy on my screen, but that's not certain. Maybe add lightness by poking some holes in it ?? You'll get there, I'm sure .. Dave BC PS My mate's daughter told me the other day that I didn't really look old. My reply was that's all very well but I don't really feel new. |
| Stilldrillin:
Hi Dave. Thanks for the birthday wishes. I guess, every day is a bonus from now on........ :thumbup: This type of engine is the same as the Robinson type. Too much heat rises to the cool end....... :scratch: Funny you should suggest a horizontal format. I tried it that way, yesterday! Still didn't work....... :( Have thought of junking the columns. But the engine is diagonal, across the platform. Not insurmountable, I'm sure! Frankly, I think the displacer/ piston ratio is not enough at 1.8. Guess we need a smaller power piston, like Robbo! :palm: Love your "not new" punchline! :clap: :clap: David D |
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